The Galileo Seven always seems padded to me. But most TOS-episodes don't bore me, even though they are very slow compared to today's shows. Must be the quality writing that keeps me from dozing off.

TNG was my first trek and I will always prefer it. But some of the episodes definitely have a tendency to become too "soap-opera" with lengthy talking-head shots.
VOY and DS9 basically had the same style and when ENT aired, the difference between that show and BSG was like night and day.

JJ-Trek is another story. Fast, faster, fastest just for fastness sake. Gotta keep that camera moving. Style over substance.